PSI - Issue 19

Kim Bergner et al. / Procedia Structural Integrity 19 (2019) 140–149 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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The results of the strain-controlled fatigue tests are shown in Fig. 8 and Fig. 9. For the calculation of the cyclic stress-strain curve parameters, the compatibility, defined in [14], can be used. These parameters are shown in Table 4.

Fig. 8. Cyclic stress strain curves and strain life curves for the bulk material (EN-GJS-400-15)

Fig. 9. Cyclic stress strain curves and strain life curves for the rim zone (GE_I and GE_II)

3. Fatigue analysis Three different fatigue approaches were applied to the bending specimens. With each approach, a component S-N curve was calculated and compared with the fatigue tests. 1. FKM guideline 2. Strain-life approach considering the rim zone in the FE analysis 3. Strain-life approach considering the rim zone factor 3.1. Description of the fatigue approaches An overview of the applied fatigue approaches can be found in Table 5. In all three approaches, the supporting effect and the influence of the roughness were considered in accordance with the FKM guideline [2]. 1. FKM guideline For the fatigue analysis using the FKM guideline the local stresses in the bending specimen were determined with a FE analysis using a linear-elastic material behavior. A homogeneous specimen was assumed in the FE analysis, i.e. no rim zone was modelled. As a basis for the fatigue assessment the tensile strength of R m = 374 MPa from [15], for the EN-GJ-400-15, is used. The mean stress sensitivity, calculated according to the FKM guideline, is M = 0.21. Since the resulting fatigue strength according to the FKM guideline is based on a survival probability of P S = 97.7 %, it is converted using a scatter band of T σ = 1.3 from P S = 97.5 % to P S = 50 %, in order to compare that with the experimental fatigue tests and the other fatigue approaches, Table 5.